1. Field of the Invention
This invention relates to the manufacture of rails. More particularly, it relates to an electronic means for measuring camber in hot rails produced in a rail mill.
In the manufacture of rails, there is a significant problem in producing a straight rail. This problem arises because of the unsymmetrical nature of a rail about an axis parallel to its base. The head of the rail, being a much larger mass than the base, cools slower and contracts more than the base. This uneven thermal contraction causes a straight hot rail to assume a curvature as it cools, with the head of the rail concave from end to end. To compensate for this curvature and thereby produce a straight rail, a camber is mechanically introduced in the rail when it is hot by imparting bending forces to it opposite to the curvature of its natural contraction.
The cambering of the rails in a rail mill is accomplished in a camber machine located up-stream of a runout table and cooling beds. The camber machine consists of a set of horizontal rolls with a vertical roll on each side of the horizontal rolls. It is set to slightly bend the rail so as to make the head or top surface of the rail convex from end to end. Since the amount of thermal contraction is a function of the rail section, the amount of camber must be adjusted to correspond to rails of different sections.
As the rails pass through the camber machine, support is provided at the exit of the machine by the runout table. From the runout table the rails pass onto the cooling beds.
2. Description of the Prior Art
To determine the amount of camber required to compensate for the contraction of a particular rail section, the practice in the past has been a very crude and inaccurate trial and error procedure. The operator of the camber machine was required to walk away from his station and onto a bridge spanning the runout table. From that vantage point he would observe chalk marks which were placed on an apron between two runout table rolls, about one rail length away, and at intervals of not less than 1/2 inch to 1 inch. If the rail was not close to the chalk mark corresponding to the camber for that rail section, he would go back to the camber console and adjust the camber to what he thought would be the proper amount. However, he would not know until approximately six hours later when the rail had cooled whether his measurement and subsequent adjustment was accurate. The distance from the bridge to the marks, the distance between the marks, and the operating conditions of the mill serve to make the chalk marks poor reference points and the system itself fraught with inaccuracies.
Those rails which were not properly cambered are crooked when they are cooled and require further processing in a gag press before they can be sold. Excessive straightening requires a considerable amount of time and expense and adds to the production costs of the rails.